package com.myself.sqlSession;

import com.myself.pojo.Configuration;
import com.myself.pojo.MappedStatement;

import javax.lang.model.type.TypeVariable;
import java.lang.reflect.*;
import java.util.List;

public class DefaultSqlSession implements SqlSession {

    private Configuration configuration;


    public DefaultSqlSession(Configuration configuration) {
        this.configuration = configuration;
    }

    @Override
    public <E> List<E> selectList(String statementid, Object... params) throws Exception {

        // 将要去完成simpleExecutor里的query方法的调用
        SimpleExecutor simpleExecutor = new SimpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementid);
        List<Object> list = simpleExecutor.query(configuration, mappedStatement, params);

        return (List<E>) list;
    }

    @Override
    public <T> T selectOne(String statementid, Object... params) throws Exception {
        List<Object> objects = selectList(statementid, params);
        if (objects.size() == 1) {
            return (T) objects.get(0);
        } else {
            throw new RuntimeException("查询结果为空或者返回结果过多");
        }

    }

    @Override
    public <T> T getMapper(Class<?> mapperClase) {
        // 使用JDK动态代理来为Dao接口生成代理对象，并返回

        Object proxyInstance = Proxy.newProxyInstance(DefaultSqlSession.class.getClassLoader(), new Class[]{mapperClase}, new InvocationHandler() {
            /*
            1.proxy：当前代理对象的应用
            2.method：当前被调用方法的引用
            3.args：传递的参数
             */
            @Override
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                // 底层都还是去执行JDBC代码 //根据不同情况，来调用selctList或者selectOne
                // 准备参数 1：statmentid :sql语句的唯一标识：namespace.id = 接口全限定名.方法名
                // 方法名：findAll
                String methodName = method.getName();
                // className:namespace
                String className = method.getDeclaringClass().getName();
                // statementid
                String statementId = className + "." + methodName;

                // 准备参数 2：params:args
                // 获取被调用方法的返回值类型
                Type genericReturnType = method.getGenericReturnType();
                // 判断是否进行了泛型类型参数化（如果有这个泛型，则返回结果是list；如果没这个泛型，则是个对象）
                if (genericReturnType instanceof ParameterizedType) {
                    List<Object> objects = selectList(statementId, args);
                    return objects;
                } else if (genericReturnType.getTypeName().equals("int") && "saveUser".equals(methodName)) {
                    return saveUser(statementId, args);
                } else if (genericReturnType.getTypeName().equals("int") && "updateUser".equals(methodName)) {
                    return updateUser(statementId, args);
                } else if (genericReturnType.getTypeName().equals("int") && "deleteUser".equals(methodName)) {
                    return deleteUser(statementId, args);
                }
                System.err.println(genericReturnType.getTypeName());
                return selectOne(statementId, args);
            }
        });
        return (T) proxyInstance;
    }

    @Override
    public int saveUser(String statementid, Object... params) throws Exception {
        // 将要去完成simpleExecutor里的insert、update、delete方法的调用
        SimpleExecutor simpleExecutor = new SimpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementid);

        int save = simpleExecutor.update(configuration, mappedStatement, params);

        return save;
    }

    @Override
    public int updateUser(String statementid, Object... params) throws Exception {
        // 将要去完成simpleExecutor里的insert、update、delete方法的调用
        SimpleExecutor simpleExecutor = new SimpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementid);

        int update = simpleExecutor.update(configuration, mappedStatement, params);

        return update;    }

    @Override
    public int deleteUser(String statementid, Object... params) throws Exception {
        // 将要去完成simpleExecutor里的insert、update、delete方法的调用
        SimpleExecutor simpleExecutor = new SimpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementid);

        int delete = simpleExecutor.update(configuration, mappedStatement, params);

        return delete;
    }

}
